In the medical field, where beneficial agents are collected, processed and stored in containers, transported and ultimately delivered through tubes by infusion to patients, there has been a recent trend toward developing materials useful for fabricating such containers and tubing without the disadvantages of currently used materials such as polyvinyl chloride. These new materials for tubings must have a unique combination of properties, so that the tubing may be used in peritoneal dialysis and I.V. administration sets, blood collection and separation devices, blood transfer devices and the like. Among these properties are the materials must be environmentally compatible, have sufficient yield strength and flexibility, have a low quantity of low molecular weight additives, have good dimensional stability and be compatible with medical, pharmaceutical, nutritional and other therapeutic solutions.
It is desirable for medical tubing for many applications to be optically transparent to allow for visual inspection of fluids in the tubing. The optically transparent tubing finds applications, for example, in I.V. administration sets, peritoneal dialysis administration sets and numerous other tubing-containing medical devices where optical clarity is required for whatever reason. Other applications (such as for the delivery of light sensitive compounds and light sensitive fluids) require the tubing to provide visual light and ultra-violet light blockers or filters. The blockers by necessity render the tubing somewhat opaque. For such tubing it is desirable to provide the necessary shielding from visible and UV light while at the same time having sufficient optical clarity to allow viewing an air bubble in fluid flowing through the tubing.
It is also a requirement that the tubing materials be environmentally compatible as a significant quantity of medical tubing is disposed of in landfills and through incineration. Further benefits are realized by using a material that is thermoplastically recyclable so that scrap generated during manufacturing may be incorporated into virgin material and refabricated into other useful articles.
For tubing that is disposed of by incineration, it is necessary to use a material that does not generate or minimizes the formation of by-products such as inorganic acids which may be environmentally harmful, irritating, and corrosive. For example, PVC may generate objectionable amounts of hydrogen chloride (or hydrochloric acid when contacted with water) upon incineration.
To be compatible with medical or dialysis solutions, it is desirable that the tubing material be free from or have a minimal content of low molecular weight additives such as plasticizers, stabilizers and the like. These components could be extracted into the dialysis or therapeutic solutions that come into contact with the material. The additives may react with the solutions or otherwise render the solutions ineffective.
Polyvinyl chloride (“PVC”) has been widely used to fabricate medical tubings as it meets most of these requirements. However, because PVC by itself is a rigid polymer, low molecular weight components known as plasticizers must be added to render PVC flexible. As set forth above, these plasticizers may leach out of the tubing and into the fluid passing through the tubing to contaminate the fluid. For this reason, and because of the difficulties encountered in incinerating PVC, there is a need to replace PVC medical tubing.
Polyolefins have been developed which meet many of the requirements of medical containers and tubing, without the disadvantages associated with PVC. Polyolefins typically are compatible with medical applications because they have minimal extractability to the fluids and contents which they contact. Most polyolefins are environmentally sound as they do not generate harmful degradants upon incineration, and in most cases are capable of being thermoplastically recycled. Many polyolefins are cost effective materials that may provide an economic alternative to PVC. However, there are many hurdles to overcome to replace all the favorable attributes of PVC with a polyolefin.
One particular polyolefin of interest is an ethylene and -olefin copolymer obtained using a single-site catalyst such as a metallocene catalyst, a vanadium catalyst or the like. Of this group of copolymers those having a density of less than about 0.915 g/cc are most desirable due to their favorable modulus of elasticity and other physical characteristics. These copolymers obtained using a single site catalyst shall be referred to as ultra-low density polyethylene (m-ULDPE). The m-ULDPE copolymers have better clarity and softness, a low level of extractables and also have fewer additives than traditional polyolefins. This is largely due to m-ULDPE having a narrow molecular weight distribution and a narrow composition distribution. The m-ULDPE is a newly commercialized resin that recently has been used in food and some medical applications. The use of m-ULDPE resins to manufacture medical tubing is the subject of commonly assigned U.S. Pat. No. 5,741,452 which is incorporated herein by reference and made a part hereof.
The '452 Patent does not disclose using a polybutadiene or a blend of various grades of polybutadiene to manufacture flexible components such as medical tubings, and semi-flexible components such as drip chambers. The present inventors have found encouraging results using polybutadienes to manufacture such flexible and semi-flexible components.
Japanese Kokai Patent Application No. Hei 2[1990]-305834 discloses a radiation-resistant polybutadiene composition containing 0.01-2 parts by weight of hindered amine in 100 parts by weight of polybutadiene. This Japanese patent application discloses using syndiotactic 1,2-polybutadiene containing 90% or more of 1,2 bonds as the polybutadiene because it has both softness and strength. The crystallinity is preferably in the range of 15-30%. The Japanese patent application further discloses molding medical devices from polybutadiene and sterilizing by exposing the medical device to radiation. Such medical devices include, for example, tubing, syringes, needle bases for syringe needles, transfusion/blood transfusion sets, blood sampling appliances, and transfusion packs containing the fluid to be transfused. This Japanese patent application does not disclose using blends of polybutadiene resins to form medical products or using solvent bonding techniques to assemble products made therefrom, or using heat treatment to enhance the performance of polybutadiene based medical product such as medical tubing for pump applications.